1. Field of the Invention
The present invention relates generally to a broadcasting service, and more particularly, to a method of managing a key used for encrypting a broadcasting service where a plurality of users exists.
2. Description of the Related Art
Recently, a mobile communication system has been developed to provide various multimedia services to users. Accordingly, there is lively discussion on a broadcast service and a multicast service to provide various content to users. Hereinafter, the broadcast and multicast service may be referred to as a “broadcasting service”.
The term broadcasting service refers to a point-to-multipoint service in which multimedia data such as image data or video data is transmitted from a single source object to a plurality of receivers in a service area through use of a unidirectional bearer service. The broadcasting service may support a broadcast mode and a multicast mode. In the broadcast mode, data is broadcasted to all users in a corresponding service area. Conversely, for the multicast service, a user subscribes to a predetermined broadcasting service or a predetermined broadcasting service group where a Service Provider (SP) exists.
However, data of the broadcasting service may be encrypted and transmitted so that the data is transferred to users who have subscribed to the broadcasting service. Consequently, the data that is encrypted and transmitted will need to be decrypted by the user. Therefore, an encryption key used when the SP encrypts the data is also shared with the user.
An encryption key used in a current Open Mobile Alliance (OMA) Digital Rights Management (DRM) system may be a single encryption key, i.e., a Content encryption Key (CEK), and when the encryption key is used in the broadcasting service, the encryption key may need to be one-to-one transmitted to users of the broadcasting service. Because the method performs one-to-one management on a CEK between a system and a terminal, the method may not flexibly manage an encryption key in a broadcasting service that a plurality of users subscribe to and withdraw from during a service time. That is, an encryption key that is used every time that a user requests a service and withdraws from the service will be continuously updated. In this process, overload on a bidirectional network often occurs.
Therefore, a need exists for a method that effectively transfers a key required for decrypting content by effectively utilizing a one-to-one bidirectional channel and a broadcasting channel.